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The Younger Dryas (YD) was a period in Earth's geologic history that occurred circa 12,900 to 11,700 years Before Present (BP). It is primarily known for the sudden or "abrupt" cooling in the Northern Hemisphere, when the North Atlantic Ocean cooled and annual air temperatures decreased by ~3 °C (5.4 °F) over North America, 2–6 °C (3.6–10.8 °F) in Europe and up to 10 °C (18 °F) in Greenland, in a few decades. Cooling in Greenland was particularly rapid, taking place over just 3 years or less. At the same time, the Southern Hemisphere experienced warming. This period ended as rapidly as it began, with dramatic warming over ~50 years, which transitioned the Earth from the glacial Pleistocene epoch into the current Holocene.
Geomorphology is the scientific study of the origin and evolution of topographic and bathymetric features generated by physical, chemical or biological processes operating at or near Earth's surface. Geomorphologists seek to understand why landscapes look the way they do, to understand landform and terrain history and dynamics and to predict changes through a combination of field observations, physical experiments and numerical modeling. Geomorphologists work within disciplines such as physical geography, geology, geodesy, engineering geology, archaeology, climatology, and geotechnical engineering. This broad base of interests contributes to many research styles and interests within the field.
A loess is a clastic, predominantly silt-sized sediment that is formed by the accumulation of wind-blown dust. Ten percent of Earth's land area is covered by loesses or similar deposits.
The Last Glacial Period (LGP), also known as the Last glacial cycle, occurred from the end of the Last Interglacial to the beginning of the Holocene, c. 115,000 – c. 11,700 years ago, and thus corresponds to most of the timespan of the Late Pleistocene.
The Last Glacial Maximum (LGM), also referred to as the Last Glacial Coldest Period, was the most recent time during the Last Glacial Period where ice sheets were at their greatest extent 26,000 and 20,000 years ago. Ice sheets covered much of Northern North America, Northern Europe, and Asia and profoundly affected Earth's climate by causing a major expansion of deserts, along with a large drop in sea levels.
The Hoxnian Stage was a middle Pleistocene stage of the geological history of the British Isles. It was an interglacial which preceded the Wolstonian Stage and followed the Anglian Stage. It is equivalent to Marine Isotope Stage 11. Marine Isotope Stage 11 started 424,000 years ago and ended 374,000 years ago. The Hoxnian is divided into sub-stages Ho I to Ho IV. It is likely equivalent to the Holstein Interglacial in Central Europe.
The Cordilleran ice sheet was a major ice sheet that periodically covered large parts of North America during glacial periods over the last ~2.6 million years.
Thermokarst is a type of terrain characterised by very irregular surfaces of marshy hollows and small hummocks formed when ice-rich permafrost thaws. The land surface type occurs in Arctic areas, and on a smaller scale in mountainous areas such as the Himalayas and the Swiss Alps.
The Holocene glacial retreat is a geographical phenomenon that involved the global retreat of glaciers (deglaciation) that previously had advanced during the Last Glacial Maximum. Ice sheet retreat initiated ca. 19,000 years ago and accelerated after ca. 15,000 years ago. The Holocene, starting with abrupt warming 11,700 years ago, resulted in rapid melting of the remaining ice sheets of North America and Europe.
Paraglacial means unstable conditions caused by a significant relaxation time in processes and geomorphic patterns following glacial climates. Rates of landscape change and sediment output from the system are typically elevated during paraglacial landscape response.
Patterned ground is the distinct and often symmetrical natural pattern of geometric shapes formed by the deformation of ground material in periglacial regions. It is typically found in remote regions of the Arctic, Antarctica, and the Outback in Australia, but is also found anywhere that freezing and thawing of soil alternate; patterned ground has also been observed in the hyper-arid Atacama Desert and on Mars. The geometric shapes and patterns associated with patterned ground are often mistaken as artistic human creations. The mechanism of the formation of patterned ground had long puzzled scientists but the introduction of computer-generated geological models in the past 20 years has allowed scientists to relate it to frost heaving, the expansion that occurs when wet, fine-grained, and porous soils freeze.
Matthias Kuhle was a German geographer and professor at the University of Göttingen. He edited the book series Geography International published by Shaker Verlag.
The Weichselian glaciation is the regional name for the Last Glacial Period in the northern parts of Europe. In the Alpine region it corresponds to the Würm glaciation. It was characterized by a large ice sheet that spread out from the Scandinavian Mountains and extended as far as the east coast of Schleswig-Holstein, northern Poland and Northwest Russia. This glaciation is also known as the Weichselian ice age, Vistulian glaciation, Weichsel or, less commonly, the Weichsel glaciation, Weichselian cold period (Weichsel-Kaltzeit), Weichselian glacial (Weichsel-Glazial), Weichselian Stage or, rarely, the Weichselian complex (Weichsel-Komplex).
A blockfield, felsenmeer, boulder field or stone field is a surface covered by boulder- or block-sized rocks usually associated with a history of volcanic activity, alpine and subpolar climates and periglaciation. Blockfields differ from screes and talus slope in that blockfields do not apparently originate from mass wastings. They are believed to be formed by frost weathering below the surface. An alternative theory that modern blockfields may have originated from chemical weathering that occurred in the Neogene when the climate was relatively warmer. Following this thought the blockfields would then have been reworked by periglacial action.
Deglaciation is the transition from full glacial conditions during ice ages, to warm interglacials, characterized by global warming and sea level rise due to change in continental ice volume. Thus, it refers to the retreat of a glacier, an ice sheet or frozen surface layer, and the resulting exposure of the Earth's surface. The decline of the cryosphere due to ablation can occur on any scale from global to localized to a particular glacier. After the Last Glacial Maximum, the last deglaciation begun, which lasted until the early Holocene. Around much of Earth, deglaciation during the last 100 years has been accelerating as a result of climate change, partly brought on by anthropogenic changes to greenhouse gases.
Bjørn Grothaug Andersen was a Norwegian professor of Quaternary geology and glaciology who made foundational contributions to glacial geology and the understanding of climate change.
Periglaciation describes geomorphic processes that result from seasonal thawing and freezing, very often in areas of permafrost. The meltwater may refreeze in ice wedges and other structures. "Periglacial" originally suggested an environment located on the margin of past glaciers. However, freeze and thaw cycles influence landscapes also outside areas of past glaciation. Therefore, periglacial environments are anywhere when freezing and thawing modify the landscape in a significant manner.
In geology and geomorphology a paleosurface is a surface made by erosion of considerable antiquity. Paleosurfaces might be flat or uneven in some cases having considerable relief. Flat and large paleosurfaces —that is planation surfaces— have higher potential to be preserved than small and irregular surfaces and are thus the most studied kind of paleosurfaces. Irregular paleosurfaces, albeit usually smaller than flat ones, occur across the globe, one example being the Sudetes etchsurfaces. In the case of peneplains it is argued that they become paleosurfaces once they are detached from the base level they grade to.
The last glacial period and its associated glaciation is known in southern Chile as the Llanquihue glaciation. Its type area lies west of Llanquihue Lake where various drifts or end moraine systems belonging to the last glacial period have been identified. The glaciation is the last episode of existence of the Patagonian Ice Sheet. Around Nahuel Huapi Lake the equivalent glaciation is known as the Nahuel Huapi Drift.
Siwan Davies FLSW is a Welsh professor of Physical Geography in the department of science at Swansea University.
References
- 1 2 3 4 5 6 7 8 9 Austin, Bill; Warren, Charles (2016). "A Special Issue Celebrating the Career of Professor Colin Ballantyne, MA, MSC, PHD, DSC, FRSE, FRSGS, a Uniquely Scottish Geomorphologist". Scottish Geographical Journal. 132 (2): 119–129. Bibcode:2016ScGJ..132..119A. doi:10.1080/14702541.2016.1157380.
- ↑ Ballantyne, Colin Kerr (October 1975). "Geomorphological and Hydrological Investigations in a High Arctic Drainage Basin" (PDF). McMaster University (macsphere.mcmaster.ca). (M.Sc. thesis)
- ↑ Diamond, Derek (2013). "Robert John Price". The Geographical Journal. 179 (2): 195–196. Bibcode:2013GeogJ.179..195D. doi:10.1111/geoj.12026.
- ↑ Byrne, Mary-Louise; Howarth, Phil (2006). "Foreword S. Brian Mccann (1935-2004)". Géographie Physique et Quaternaire. 60: 7. doi:10.7202/016359ar.
- 1 2 3 4 "Prof. Colin Ballantyne". Scottish Alliance for Geoscience, Environment and Society (SAGES).
- ↑ Ballantyne, Colin Kerr (1981). "Periglacial landforms and environments on mountains in the Northern Highlands of Scotland".
- ↑ Smith, David; Robinson, Marie (13 February 2018). "Obituary: Brian Sissons, earth scientist who contributed hugely to understanding the Scottish landscape". The Scotsman.
- ↑ Fabel, Derek; Ballantyne, C. K.; Xu, Sheng (2012). "Trimlines, blockfields, mountain-top erratics and the vertical dimensions of the last British–Irish Ice Sheet in NW Scotland". Quaternary Science Reviews. 55: 91–102. doi:10.1016/j.quascirev.2012.09.002.
- ↑ Kendall, Christopher G. "review of The Periglaciation of Great Britain by C. K. Ballantyne and Charles Harris" (PDF). Society for Sedimentary Geology (formerly the Society of Economic Paleontologists and Mineralogists), SEPM (sepmstrata.org).
- ↑ Jack, Chris (31 May 2021). "review of Scotland's Mountain Landscapes: A Geomorphological Perspective by Colin K. Ballantyne". Geoscientist: The Magazine of the Geological Society of London (Geoscientist.online).
